Answer:
The mass number of an atom is its total number of protons and neutrons. Atoms of different elements usually have different mass numbers , but they can be the same. For example, the mass number of argon atoms and calcium atoms can both be 40.
Explanation:
Scientist study index fossils so they will get an understanding of what life was like back then.
Answer:Vacuole
Explanation:Vacuoles basically do the functions of storage, ingestion, digestion, etc.